Specific Aims: 1. To investigate the genetic control of initiation of muscle-specific protein synthesis in single myogenic cells. 2. To investigate the genetic control of cell division in the terminal stages of skeletal myogenesis. 3. To develop a method for producing large number of myogenic precursor cells, all at the same stage of differentiation. 4. to analyze differences in the types of proteins synthesized by different classes of myogenic precursor cells. Methodology: 1. Cell culture; cloning of myogenic cells from the chick embryo. 2. Immunocytochemistry. 3. Protein isolation, purification, and characterization. Long-term Objectives: 1. To provide a basic understanding of the events in skeletal myogenesis at the level of singe precursor cells and their progeny. 2. To determine what decisions are made by cells as they transit through the myogenic lineage. 3. These data will permit a proper application and interpretation of biochemical and molecular biological approaches to myogenesis. Health-Relatedness: 1. Data from this study will provide a cell-biological framework within which to approach more fruitfully the problems of muscle disease and muscle regeneration.